Large fires or fires in remote locations are often fought using aircraft to drop chemical fire retardants or water either directly on the fire or at nearby locations to create a fire break. Helicopters are often used for such operations because they do not require a dedicated landing strip and more importantly because they can fill their fire-fighting bucket without the need to land the helicopter. Typically, the bucket can be filled at a nearby body of water which may include a lake, dam, river or even a swimming pool. Having the ability to fill the bucket in this way reduces the time between water drops, hopefully resulting in the fire being extinguished more quickly. Filling the bucket locally also saves fuel and other running costs which can be extremely expensive.
U.S. Pat. No. 5,829,809 describes a bucket for use with an aircraft which permits dumping of two or more separate loads of water for a single fill of the bucket. The apparatus has an outer bucket with an outer dump valve and an inner bucket with an inner dump valve. The inner bucket is located within the outer bucket and a space is established therebetween to provide a clearance to receive water. The dump valves are flexible sleeves which are operable independently of each other and in sequence so that the outer dump valve is opened before the inner dump valve. As evident from the Figures of U.S. Pat. No. 5,829,809, the illustrated apparatus includes significant rigging and lines to control the operation of the valves. Such rigging and lines may be easily fouled resulting in the inability to release water from the bucket and in an extreme situation this may result in the decision to jettison the bucket. Buckets according to U.S. Pat. No. 5,829,809 also have a tendency to leak due to the inner dump valve not sealing correctly, the purse strings are very prone to wear and tend to have a poor drop pattern due to the inner dump valve flailing in the wind when the water is jettisoned. This type of bucket is also very prone to sailing, causing the bucket to move from substantially below the helicopter when full to very close to the tail rotor when empty. This is potentially very dangerous.
U.S. Pat. No. 6,192,990 describes a fire-fighting bucket including a valve 18 for controllably releasing a stream of fluid over a fire. As best shown by a comparison of FIGS. 3 and 4, the valve 18 releases water from the bucket when the solid side wall 60 of the valve 18 is raised vertically (FIG. 4) away from the base plate 40. Valve 18 is controlled by a complicated control head suspended above the bucket. Further, the valve 18 is very large and thus takes up a lot of space inside the bucket reducing the bucket's water carrying capacity. The valve seals are very difficult to replace and the bucket is very heavy. Accordingly, the bucket is very difficult to transport, store and load into an aircraft.
The applicant's earlier Australian patent application 2005225146 identified various problems associated with different fire-fighting buckets and also the valves used in such buckets. That application further described a valve used to control the release of water from a fire-fighting bucket. The valve 1 is located within body 10 and is operated by a liner screw motor that can be controlled to close the sealing plates 7 against their respective ports 19. As apparent from FIG. 4, the body 10 is quite large and the ports 19 are located above the base of the bucket. Accordingly, even if the walls of the bucket 20 are capable of collapse, the size and configuration of the valve, which is not collapsible, makes transport and storage of the bucket 20 problematic.
U.S. Pat. No. 6,125,942 describes a fire-fighting system that uses a bucket suspended from a helicopter to deposit a fire retardant onto the fire. More particularly, U.S. Pat. No. 6,125,942 describes a bucket with a valve for varying the characteristics of the flow that is discharged from the bucket's opening. FIGS. 8 and 9 illustrate a fast-acting valve 206 that includes a top plate 208 that rotates on a shaft 210. The top plate 208 has openings 212 that can be aligned, upon rotation of the top plate 208, with openings 220 in a lower plate 222 fixed in the bottom of the bucket. FIG. 10 illustrates an alternative valve 306. The valve 306 adopts a clam shell configuration, in which two cylindrical flaps 308, 310 are hinged at their axis of rotation to a shaft 312. The valve arrangements described in U.S. Pat. No. 6,125,942 suffer from a number of disadvantages including high valve wear due to friction on the valve seal, poor flow control of water through the valve and considerable valve opening and closing lag time.
The present invention seeks to provide an improved fire-fighting bucket and related components thereof.
The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of this application.